Cast alloy



United States Patent 3,220,829 CAST ALLOY Murray T. Stewart, Fanwood, and Clarence G. Bieher, Roselle Park, N.J., assignors to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 10, 1961, Ser. No. 144,069 5 Claims. (Cl. 75-171) The present inv'ention relates to nickel-chromium alloys and, more particularly, to nickel-chromium alloy castings particularly adapted to be employed at service temperatures up to about 1350 F.

Heretofore, the art has endeavored to provide cast alloys having high strength and ductility at room temperature in combination with high strength, creep resistance and duetility at elevated temperatures of the order of 1300 F. and higher. In addition, in order to be commercially practicable, the alloys must be amenable to be melted in air or under imperfect protective atmospheres and must be adapted to be cast not only in specially formulated precision casting mold media but also in commonly available foundry sand molds. Although attempts were made to provide alloys exhibiting the foregoing combination of advantageous characteristics, none, as far as we are awar'e, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that by particularly correlating amounts of chromium, cobalt, molybdenum, columbium, boron and zirconium in a nickel base, alloys can be provided which possess an outstanding combination of characteristics including room temperature and elevated temperature strength and ductility.

It is an object of the present invention to provide a novel alloy amenable to being melted in air and being cast by usual foundry procedures.

Another obj'ect of the invention is to provide a novel cast alloy having an outstanding combination of room temperature and elevated temperature characteristics.

The invention also contemplates providing castings particularly adapted to be employed at service temperatures of the order of 1200 F. and higher.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates alloys containing in per cent by weight about 1 0% to about 20% chromium, about 5% to about 20% cobalt, about 6% to about 10% columbium, about 0.5% to about 3.50% molybdenum, up to about 0.25% carbon, up to about 12% iron, up to about 0.1% boron, up to about 0.5% zirconium, up to about 1% vanadium, up to about 1% silicon, with the balance being essentially nickel together with small amounts of impurities and deoxidants normally associated therewith. The alloys of the present invention usually, and advantageously, contain about 0.0001% to about 0.01% boron, about 0.001% to about 0.5 carbon, up to about 0.3% silicon, up to about 4% iron and up to about 0.05% zirconium.

In making alloys in accordance with the present invention, normal foundry methods of melting and casting can be employed. For example, the alloys can be prepared in air or an inert atmosphere by first melting the required nick'el and cobalt, adding the required chromium, molybdenum and columbium (and incidental tantalum), thereafter adding the desired zirconium and boron, and finally, deoxidizing with about 0.1% by Weight of calcium silicide.

3,220,820 Patented Nov. 30, 1965 The molten alloy is then poured into molds and allowed to solidify in air. The master alloy thus produced is then remelted and cast in standard foundry molds to produce castings of the desired size and shape. Any of the usual casting methods can be employed, including sand casting, shell casting, investment casting, etc. It is important that elements such as aluminum and titanium be kept at as low percentage levels as possible and should ordinarily not be present in amounts more than about 0.1% in the aggregate.

In carrying the invention into practice, it is advantage ous to maintain the columbium in the alloys from about 7% to about 9%. In this regard, it is to be observed that any tantalum accompanying the columbium is to be treated as columbium for compositional purposes. The alloys of the present invention advantageously contain at least about 2.5% molybdenum. In addition, alloys containing about 12% to about 16% of either chromium or cobalt exhibit an advantageous combination of character istics. After the alloys have been cast, it is advantageous to subject the resultant castings to a heat treatment comprising a solution treatment at about 2000 F. to about 2100 F. for about 1 to about 8 hours and an aging treatment at about 1500 F. to about 1100 F. for about 1 to about 1 00 or even longer hours. Furnac'e cooling or controlled sloW cooling through the range of 1500 F. to about 1100" F. or any part thereof can effectively substitute for all or part of said aging treatment. Under certain circumstances the cast alloy can be aged directly without solution heat treatment. Particularly suitable heat treatments are set forth in Table I:

Table I Heat Solution Treatment Aging Treatment Treatment No. Temp, Time Temp, Time (hours) F. (hours) F.

A 2,050 4 1, 350 16 plus cool at 50 F. per

hour to 1,l50 F. B 2, 050 4 1,350 6. O 2, 050 4 1, 350 16 plus cool at 25 F. per

hour to 1,150 F.

For the purpose of giving those skilled in the art a better understanding of the invention, illustrative examples of alloys within the scope of the present invention are set forth in Table II:

1 Balance including small amounts of carbon, silicon, manganese, etc. 2 Amounts added.

Each of the cast alloys set forth in Table II were solution treated at 2050 F. for 4 hours. After aging, the alloys exhibited mechanical characteristics such as yield strength (Y.S.) in pounds per square inch (p.s.i.), ultimate tensile strength (U.T.S.), elongation (El.) and reduction in area (R.A.) as set forth in Table III:

1 Room temperature.

Stress-rupture tests of cast, heat treated alloys within the ambit of the present invention conducted at 1350 F. give results as set forth in Table IV:

Table IV Heat El. per- Alloy N 0. Treat- Stress, Time, cent in 11.11.,

merit p.s.i. Hours one inch percent Alloys of the present invention have good rupture strength at temperatures below 1300 F. For example, at 1200 F., alloy No.4, when heat treated by heat treatment A- (see Table I), broke after 251 hours at a stress of 95,000 p.s.i. with 2.4% elongation and 7% reduction in area.

The present invention is particularly applicable to the production of cast parts, compon'ents, etc., employed at temperatures up to about 1300 F. Such parts, components, etc., include extrusion dies, gas turbine rotors, aircraft hardware, paper mill components, etc.

Although the present invention has been described in conjunction with preferred embodiments, it is to be under stood that modifications and variations may be resorted to Without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. A casting for use at elevated temperatures up to about 1350 F. consisting essentially, in percent by weight,

of about 10% to about 20% chromium, about 5% to about 20% cobalt, with the proviso that at least one of the elements from the group consisting of chromium and cobalt is present in the range of about 12% to about 16%, about 6% to about 10% columbium, about 0.5% to about 3.50% molybdenum, up to about 0.25% carbon, up to about 12% iron, up to about 0.1% boron, up to about 0.5% zirconium, up to about 1% vanadium, up to about 1% silicon with the balance being essentially nickel, said casting containing not more than 0.1% of metal from the group consisting of aluminum and titanium.

2. A casting as defined in claim 1 wherein the columbium is about 7% to about 9% 3. A casting as defined in claim 1 wherein the molybdenum is about 2.5% to about 3.50%.

4. A casting for use at elevated temperatures up to about 1350" F. consisting essentially, in percent by weight, of about 12% to about 16% chromium, about 12% to about 16% cobalt, about 7% to about 9% columbium, about 2.5% to about 3.50% molybdenum, up to about 0.05% carbon, up to about 12% iron, about 0.0001% to about 0.01% boron, up to about 0.05% zirconium, up to about 0.3% silicon, not more than 0.1% total aluminum plus titanium, with the balance being essentially nickel.

5. A casting for use at 'elevated temperatures up to about 135 0 F. consisting essentially, in percent by weight, of about 10% to about 15% chromium, about 7% to about 15 cobalt, about.8% to about 9.5% columbium, about 3% molybdenum, about 3% to about 10% iron with the balance being nickel together with small amounts of deoxidants, impurities, incidental 'elements normally associated therewith and not more than about 0.1% total aluminum plus titanium, said casting being characterized in the solution treated and aged condition by room temperature tensile strength of at least about 153,600 pounds per square inch.

References Cited by the Examiner UNITED STATES PATENTS 2,246,078 6/ 1,941 Rohn et a1. 75-171 2,247,643 7/1941 Rohn et al. 75171 2,981,621 4/ 1961 Thielemann 75171 3,046,108 7/ 1962 Eiselstein 75--171 3,069,258 12/1962 Haynes 75171 FOREIGN PATENTS $1 0,154 7 1939 Great Britain. 674,027 6/ 1952 Great Britain.

HYLAND BIZOT, Primary Examiner.

DAVID L. RECK, WINSTON A. DOUGLAS,

Examiners. 

1. A CASTING FOR USE AT ELEVATED TEMPERATURES UP TO ABOUT 1350*F. CONSISTING ESSENTIALLY, IN PERCENT BY WEIGHT, OF ABOUT 10% TO ABOUT 20% CHROMIUM, ABOUT 5% TO ABOUT 20% COBALT, WITH THE PROVISO THAT AT LEAST ONE OF THE ELEMENTS FROM THE GROUP CONSISTING OF CHROMIUM AND COLBALT IS PRESENT IN THE RANGE OF ABOUT 12% TO ABOUT 16%, ABOUT 6% TO ABOUT 10% COLUMBIUM, ABOUT 0.5% TO ABOUT 3.50% MOLYBDENUM, UP TO ABOUT 0.25% CARBON, UP TO ABOUT 12% IRON, UP TO ABOUT 0.1% BORON, UP TO ABOUT 0.5% ZIRCONIUM, UP TO ABOUT 1% VANADIUM, UP TO ABOUT 1% SILICON WITH THE BALANCE BEING ESSENTIALLY NICKEL, SAID CASTING CONTAINING NOT MORE THAN 0.1% OF METAL FROM THE GROUP CONSISTING OF ALUMINUM AND TITANIUM. 